1. Field of the Invention
The present invention relates to a sheet conveying system and a control method therefor as well as a control program and a storage medium, and more particularly to a sheet conveying system including respective sheet conveying devices of an image forming apparatus, such as a copying machine, a printer, or a facsimile, and sheet post-processing apparatuses, such as a finisher, a stacker, and a bookbinding apparatus, and a control method therefor as well as a control program for implementing the method and a storage medium storing the program.
2. Description of the Related Art
In a sheet conveying device for an image forming apparatus, when a sheet passes between two sensors arranged in a conveying path of the sheet conveying device, unless the sheet passes one of the sensors before a predetermined time period elapses after passing the other, or unless one of the sensors detects the absence of the sheet before a predetermined time period elapses after the sensor has detected the presence of the sheet, it is determined that jamming has occurred.
When such jamming has occurred, the image forming apparatus suspends all operations of the image forming process, displays on a display section a location where the jamming has occurred and a method of coping with the jamming, requests the user to carry out an operation for removing the jammed sheet, and resumes the suspended operations of the image forming process after detection of removal of the jammed sheet.
When the sheet is passed from a sheet conveying device of an image forming apparatus (upstream apparatus) to a sheet conveying device of a sheet post-processing apparatus (downstream apparatus), if jamming has occurred in the upstream apparatus, the upstream apparatus stops the conveyance of the sheet, but a jammed sheet, which has entered the downstream apparatus, is sometimes drawn out from the upstream apparatus by conveying rollers of the downstream apparatus. In this case, the downstream apparatus conveys the drawn-out jammed sheet as it is to a designated conveyance destination of processed sheets.
The upstream apparatus determines that the jammed sheet has been removed by the removal operation 0of the user, and resumes the image forming process by forming an image on a sheet corresponding to the jammed sheet. In actuality, however, the sheet corresponding to the jammed sheet has been stacked e.g. on an intermediate tray as one of the processed sheets, and hence if the image forming process is immediately resumed, another sheet corresponding to the jammed sheet is mixed with the processed sheets.
To avoid the above inconvenience, there have been proposed a method of rejecting all the processed sheets having a jammed sheet mixed therewith, discharging the entire sheet bundle into another stack tray, and resuming the image forming process from a first sheet of the sheet bundle (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. 2004-058354), and a method of causing the user to eliminate a jammed sheet stacked on an intermediate tray.
The first-mentioned conventional techniques, however, rejects all the stacked sheets of the bundle having the jammed sheet mixed therewith, and resumes the image forming process from the first sheet of the bundle, so that the image forming process has to be carried out on an increased number of sheets in a duplicating manner, which increases waste in time as well as resources, such as sheets and toners.
Further, in the second-mentioned conventional technique, since the sheet bundle stacked on the intermediate tray is held by registration plates and rollers, it is difficult for the user to remove the jammed sheet alone without displacing the bundle.